Biomedical subjects

R C Mellon

Publications and source records attributed to R C Mellon.

4 recordsLinked to original sources

PubMed1991

Development of intersensory function: age-related differences in stimulus selection of multimodal compounds in rats as revealed by Pavlovian conditioning.

Preweanling and adult rats were exposed to Pavlovian stimulus pairings with lights, tones, and light-tone compounds as conditional stimuli (CSs). Tone intensity was varied. As was found in previous studies using flavor CSs, odor CSs, or both, in which significant overshadowing or potentiation occurred to an element of a compound, overshadowing was less likely and potentiation more likely for preweanlings than for adults. Several experiments supported the view that these effects reflect an age-related difference in the controlling properties of stimuli: Young rats are more disposed to encode multimodal compounds on the basis of amodal intensity, whereas their elders are more likely to encode modality-specific properties of light and sound. Differential reinforcement in the presence of lights, tones, and light-tone compounds made preweanlings' stimulus selection appear more adultlike and may be a cause of development of intersensory function.

Aging↗

PubMed1990

Delay and number of food reinforcers: Effects on choice and latencies.

Pigeons were given a choice between two identical-duration situations (terminal links of chain schedules). One terminal link of the choice pair provided two food deliveries, and the other provided five. The exact times of these food deliveries differed between the terminal links and were varied over conditions. A single response during the initial link gave immediate access to the corresponding terminal link. Forced trials, during which only one of the initial-link keys was lighted, were interspersed with choice trials during which both initial-link keys were lighted. Choice tended to favor whichever terminal link was correlated with the higher sum of the immediacies (i.e., the sum of the reciprocals of the delays to each of the reinforcers following the choice, with all delays measured from the choice). Latencies on forced trials and on choice trials also were related (negatively) to the sum of the immediacies. This correlation among response measures (choice and latencies) suggests that both measures are manifestations of the effect of conditioned reinforcement on response tendencies.

Journal Article↗

PubMed1989

Dynamic organization of intersensory function.

Issues related to infant intersensory functioning are reviewed. The argument is offered that limitations of sensory inputs during early stages of development are necessary and provide structure and organization which determine behavioural characteristics at later stages. It is also suggested that infant organisms respond to the intensity of stimulation rather than organizational characteristics and that this is responsible for the form of sensory equivalence apparent during early development. A scheme for the investigation of sources of intersensory organization is presented which involves a prospective analysis of how consideration of the times of onset of sensory functions helps us to understand intra- and intersensory development. The advantages of this experimental approach are outlined.

Arousal↗

PubMed1986

Resistance to change produced by access to fixed-delay versus variable-delay terminal links.

Pigeons' responding was reinforced on a multiple schedule consisting of two two-link chain schedules presented in regular alternation. Responding in initial links (always variable-interval 60-s) produced a key-color change and access to a terminal link. The terminal link for one chain provided food after a fixed delay (fixed-interval or fixed-time); the terminal link for the other provided food after a variable delay (variable-interval or variable-time). The average duration of the terminal-link schedules was varied across conditions, but in every condition the arithmetic mean of the variable-delay terminal-link schedule was equal to the duration of the fixed delay. Response rates were higher in the initial links of the chains with the variable-delay terminal links. Response-decreasing operations (satiation, extinction) were used after performances reached asymptote. Response rates maintained by access to variable-delay terminal links tended to be more resistant to change than were rates maintained by access to fixed-delay terminal links. These results are consistent with the preference for variable- over fixed-interval terminal links observed with concurrent-chains schedules, suggesting (1) that immediacy of reinforcement influences the conditioned reinforcing potency of access to a terminal link and (2) that choice in concurrent chains and resistance of responding to change may be manifestations of the same effect of reinforcement.

Journal Article↗